There is currently considerable growth in the development of golf club heads of improved performance, particularly with the benefit of lighter weight. Analyzing this move from the facet of development of materials, the following golf club heads have been proposed. However, none of them have fully satisfactory performance.
(i) Japanese Utility Model Application Laid-Open No. 22755/1976 discloses a golf club head having a face plate, which is made of an alumina ceramic material containing at least 90% Al.sub.2 O.sub.3, applied to the face with a view toward achieving a head weight reduction and also providing increased resilience against the ball. The ball however tends to slip when struck, because the face is a smooth surface formed singly of the alumina ceramic material mentioned above. The above golf club head is accompanied by another drawback in that the face plate is prone to separation from the face of the head because they are merely bonded face to face two-dimensionally.
(ii) Japanese Patent Application Laid-Open No. 198170/1985 discloses a golf club head with a casting of Al or an Al alloy in a foamed metal body (metal sponge body) composed principally of Ni, for the ball-striking face of the head, to reduce weight and improve hardness, resilience, abrasion resistance and machinability. The casting is however a foamed metal body and hence has a small effect for the reduction of weight. Furthermore, the foamed metal body forming the ball-striking face and a member forming other portions of the head are made of similar metal materials, so that there is little difference in hardness between them. It is impossible therefore to spin the ball when striking it. In other words, the above golf club head cannot give any large traction to the ball, thereby making it difficult to impart the desired flying characteristics to the ball when striking it.
(iii) Japanese Utility Model Application Laid-Open No. 25457/1978 discloses a golf club head which is composed of a sponge metal impregnated with a synthetic resin. Because of the use of the sponge metal, the head has a large specific gravity. Therefore, this approach does not contribute much to achieving a lighter head. It is hence impossible to fabricate the large head desirable to facilitate striking the ball.
It is therefore an object of the present invention to avoid the drawbacks of the above-discussed golf club heads, especially the conventional club heads' need to reduce the weight thereof.
It is another object of this invention to provide a golf club head which is lightweight, yet strong and abrasive resistant by having the golf club head composed of a foamed porous ceramic body (hereinafter, referred to as "ceramic sponge body") as a base and a metal, fiber-reinforced metal (FRM), resin or fiber-reinforced resin (FRP) filled in the ceramic sponge, instead of employing a conventional metal sponge; namely, a sponge metal produced by adding foaming agent to a molten metal.